Trace Based Sampling Log Filter Implementation

[rads-1996]

Description

Implement open-telemetry/opentelemetry-specification#4612 to filter logs based on trace_based_sampling parameter.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

[Copilot]

Pull Request Overview

This PR implements log filtering capabilities for the Azure Monitor OpenTelemetry exporter, adding support for minimum severity level filtering and trace-based sampling. The implementation allows logs to be filtered out based on their severity level or association with unsampled traces.

Key changes:

• Added two new filtering functions: _is_less_than_minimum_severity_level and _should_drop_logs_for_unsampled_traces
• Modified _log_to_envelope to return None for filtered logs instead of always returning a TelemetryItem
• Added comprehensive test coverage for both filtering mechanisms

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

File	Description
_exporter.py	Modified log export logic to filter envelopes and handle None returns from conversion function
_utils.py	Added two utility functions for severity level and trace-based filtering logic
_constants.py	Added environment variable constants for the new filtering features
test_logs.py	Added comprehensive test cases for severity filtering, trace-based filtering, and combined filtering

Comments suppressed due to low confidence (1)

sdk/monitor/azure-monitor-opentelemetry-exporter/azure/monitor/opentelemetry/exporter/export/logs/_exporter.py:201

• The Event telemetry path (lines 189-201) lacks filtering logic that is present in Exception and Message telemetry paths. Event telemetry should also be filtered based on trace-based sampling and minimum severity level for consistency. Consider adding the same filtering checks after line 201.

    elif _log_data_is_event(log_data):  # Event telemetry
        _set_statsbeat_custom_events_feature()
        envelope.name = "Microsoft.ApplicationInsights.Event"
        event_name = ""
        if log_record.attributes.get(_MICROSOFT_CUSTOM_EVENT_NAME):  # type: ignore
            event_name = str(log_record.attributes.get(_MICROSOFT_CUSTOM_EVENT_NAME))  # type: ignore
        else:
            event_name = _map_body_to_message(log_record.body)
        data = TelemetryEventData(  # type: ignore
            name=event_name,
            properties=properties,
        )
        envelope.data = MonitorBase(base_data=data, base_type="EventData")

[JacksonWeber]

Discussed with Hector, and let's align on using the configuration option for trace-based log sampling. We can also remove the addition of minimum-severity based log sampling for now and await the upstream changes. The relevant Node.js PR making this change is: Azure/azure-sdk-for-js#28993

[github-actions]

API Change Check

APIView identified API level changes in this PR and created the following API reviews

azure-monitor-opentelemetry

[hectorhdzg]

LGTM